(1) Field of the Invention
The present invention relates to a battery having a high performance, which comprises a polymeric compound having conjugated double bonds in the main chain as at least one electrode, wherein a specific nitrile compound is used as the solvent in an electrolytic solution.
(2) Description of the Prior Art
It is known that an acetylene high polymer prepared by polymerizing acetylene by using a so-called Ziegler-Natta catalyst comprising a transition metal compound and an organometallic compound exhibits an electrical conductivity falling within the semiconductor region and is therefore useful as an electrical or electronic element material. As means for preparing practical shaped articles of acetylene high polymers, there are known the following methods.
(A) A method in which a powdery acetylene high polymer is compression-molded.
(B) A method in which under specific polymerization conditions, polymerization is carried out to prepare a film of an acetylene high polymer having a fibrous microcrystalline (fibril) structure and having a high mechanical strength (see Japanese Examined Patent Publication No. 32,581/73).
It also is known that when a shaped article of the powdery acetylene high polymer prepared according to the method (A) is chemically treated with an electron-accepting compound (electron acceptor) such as BF.sub.3, BCl.sub.3, HCl, Cl.sub.2, SO.sub.2, NO.sub.2, HCN, O.sub.2 or NO, the electrical conductivity is increased about 1,000 times at the highest, and in contrast, when the shaped article is treated with an electron-donating compound (electron donor) such as ammonia or methylamine, the electrical conductivity is reduced to about 1/10,000 in an extreme case [D. J. Berets et al., Trans. Farady Soc., 64, 823 (1968)].
Furthermore, it is known that when the filmy acetylene high polymer prepared according to the method (B) is chemically doped with an electron-accepting compound such as I.sub.2, Cl.sub.2, Br.sub.2, ICl, IBr, AsF.sub.5, SbF.sub.5 or PF.sub.6 or an electron-donating compound such as Na, K or Li, the electrical conductivity of the acetylene high polymer can freely be controlled within a broad range of from 10.sup.-8 to 10.sup.+3 .OMEGA..sup.-1 .multidot.cm.sup.-1 [J.C.S. Chem. Commu., 578 (1977), Phys. Rev. Lett., 39, 1098 (1977), J. Am. Chem. Soc., 100, 1013 (1978) and J. Chem. Phys., 69, 5098 (1978)]. It has already been proposed that this doped filmy acetylene high polymer is used as a material of a positive electrode of a primary battery [Molecular Metals, NATO Conference Series, Series VI, 471-489 (1978)].
In addition to the above-mentioned chemical doping method, there has already been developed a method in which a p-type or n-type electrically conductive acetylene high polymer is prepared by electrochemically doping an acetylene high polymer with an anion such as ClO.sub.4.sup.-, PF.sub.6.sup.-, AsF.sub.6.sup.-, AsF.sub.4.sup.-, CF.sub.3 SO.sub.3.sup.- or BF.sub.4.sup.- or a cation such as R'.sub.4 N.sup.+ (in which R' stands for an alkyl group) [J.C.S. Chem. Commu., 1979, 594, C & EN, Jan. 26, 39 (1981) and J.C.S. Chem. Commu., 1981, 317]. A rechargeable battery comprising an acetylene high polymer film prepared according to the method (B), which is electrochemically doped, has been reported [Paper Presented at the International Conference on Low Dimensional Synthetic Metals, Hersinger, Denmark, 10-15, August 1980]. This battery comprises as positive and negative electrodes two acetylene high polymer films having a thickness of, for example, 0.1 mm, which are obtained according to the method (B). When this battery is immersed in a tetrahydrofuran solution containing lithium iodide and is connected to a 9-V direct current power source, lithium iodide is electrolyzed, and the acetylene high polymer film as the positive electrode is doped with iodine and the acetylene high polymer film as the negative electrode is doped with lithium. This electrolytic doping corresponds to the charging step. If a load is connected to the two doped electrodes, the lithium ion is reacted with the iodine ion and an electric power can be taken out. In this case, the open circuit voltage (Voc) is 2.8 V and the short circuit current density is 5 mA/cm.sup.2. When a tetrahydrofuran solution containing lithium perchlorate is used as the electrolyte, the open circuit voltage is 2.5 V and the short circuit current density is about 3 mA/cm.sup.2.
Since the above-mentioned battery is formed by using as the electrode material an acetylene high polymer which is capable of providing a light-weight and small-size battery, this battery has attracted attentions as a cheap battery having a high density, the weight and size of which can easily be diminished. However, propylene carbonate, tetrahydrofuran or acetonitrile used as the organic solvent of the electrolytic solution in the conventional techniques disclosed in the above-mentioned prior art references has a relatively narrow range of the stable voltage, and therefore, decomposition or polymerization is readily caused at the step of charging or discharging the battery, resulting in reduction of the energy density, the charging-discharging efficiency, the discharge voltage levelness and the charging and discharging cycle number. Furthermore, the self-discharge rate of the battery is increased. Accordingly, development of a cheap battery comprising an organic solvent having a broad range of the stable voltage, the weight and size of which can be diminished, has been eagerly desired in the art.